Rate responsive, stretchable devices further improvements

ABSTRACT

Rate-dependent, elastically-deformable devices according to various embodiments can be stretched and recovered at low elongation rates. Yet they become stiff and resistive to stretching at high elongation rates. In one embodiment, a rate-dependent, elastically-deformable device includes an elastically-deformable confinement member; one or more filaments placed inside the elastically-deformable confinement member; and a fluid that substantially fills the remaining volume inside the elastically-deformable confinement member. The resistance force to extension of the device is designed to increase as the extension rate of the device increases. At low elongation rates the filaments can readily slide past each other. At high elongation rates, the fluid transforms to a less flowable material that greatly increases the force and energy required for elongation; or transforms to a non-flowable material that resists elongation. The devices thus can be stretched and recovered at low elongation rates, but become extremely stiff and resistive to stretching at high elongation rates.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part (CIP) of U.S. patentapplication Ser. No. 13/927,985 filed Jun. 26, 2013, which in turnclaims the benefit of U.S. Provisional Patent Application No. 61/670,430filed Jul. 11, 2012. Additionally, this application claims the benefitof U.S. Provisional Patent Application No. 62/207,689, filed Aug. 20,2015. Each of the aforementioned patent applications is hereinincorporated by reference in its entirety for all purposes.

GOVERNMENT INTEREST

The invention described herein may be manufactured, used and licensed byor for the U.S. Government without the payment of royalties thereon.

BACKGROUND OF THE INVENTION

Field

Embodiments of the present invention generally relate to elastic orresilient mechanical devices, and in particular to rate-dependent,elastically-deformable devices.

Description of Related Art

Springs and elastic bands are used in a range of mechanical andassistive devices to provide resilient elastic force. For example, kneebraces typically made out of stretchable fabrics or external linkagespermit some motion to the knee, but do not effectively restrict rapidmotions that can lead to injury. Many joint injuries are associated withrapid twisting and translations of limbs and joints, such as slipping,stepping in a hole, landing from a jump, or planting a foot whilechanging direction. In fact, musculoskeletal injuries (i.e. twistedknees, ankles, and back injuries) account for 82% of lost time amongmilitary personnel. Many of these injuries are associated with dynamicactivities such as airdrops or jumping out of vehicles. These injuriesmay be further exacerbated by the approximately 100 lbs of weight inadditional equipment that a soldier or warfighter may be wearing orcarrying.

SUMMARY OF THE INVENTION

Rate-dependent, elastically-deformable devices according to variousembodiments can be stretched and recovered at low elongation rates. Yetthey become stiff and resistive to stretching at high rates.

In one embodiment, the rate-dependent, elastically-deformable deviceincludes an elastically-deformable confinement member; one or morefilaments placed inside the elastically-deformable confinement member;and a fluid that substantially fills the remaining volume inside theelastically-deformable confinement member. The resistance force toextension of the device is designed and configured to increase as theextension or elongation rate of the device increases. At low rates thefilaments can readily slide past each other. At high rates, the fluidtransforms to a less flowable material that greatly increases the forceand energy required for increased elongation; or transforms to anon-flowable material that resists further elongation.

The elastically-deformable confinement member may be formed of rubber,silicone, elastomer, fluoroelastomer, urethane, natural latex, syntheticlatex, polymer, or thermoplastic elastomer, for example. In someembodiments, the elastically-deformable confinement member is astretchable tube, which may be approximately 0.01-100 mm in diameter inan initial undeformed state. Moreover, the elastically-deformableconfinement member may include spiral wound material or folded materialin order to facilitate elastic deformation. The elastically-deformableconfinement member might further include material or one or more layersor additives to prevent puncturing by the enclosed filaments. The fluidis contained inside the elastically-deformable confinement member bymeans of crimps, plugs, barbs, melted ends, heat-crimped ends, glueand/or adhesives to name a few examples. Ends of theelastically-deformable confinement member may be able to engage and/ormay further include an end effector for attaching to an object externalto the device. The end effector may include, for instance, a crimp,clamp, spring clip, threaded fastener, snap-on fastener, glue and/oradhesive.

The one or more filaments may be formed, for instance, of steel,polymer, glass, or carbon. They can be approximately 0.001-10 mm indiameter, and can be monofilament or multifilament, twisted, untwistedor braided. In some embodiments, the one or more filaments are flat,flexible elements. Also, the filaments may include a helical shape; awavy shape; a square shape; a triangular shape; a sawtooth shape; or asinusoidal shape; and/or at least one crimp, barb, bump, or ridge, tofurther encourage interaction during shear. Ends of the one or morefilaments can be modified to inhibit puncturing through the confinementmember, where the filament end modifications may include rigid, smoothballs; compression sleeves; soft coatings; filament loops; low-frictioncoatings; and guide bushings or washers. At least one end of the one ormore filaments may be attached to the confinement member in someembodiments.

The fluid may be a non-Newtonian fluid, in some embodiments, such as ashear thickening fluid (STF). In some instances, the fluid may comprisea suspension including solid particles in a liquid, with the particlesbeing composed of polymers, ceramics, metals, silica, alumina, titania,clay, calcium carbonate and the liquid being water, an oil, a polymericliquid, a glycol, a fluorofluid, or glycerin. In other embodiments, thefluid may be an electrorheological fluid, and the device is furtherconfigured to provide an electric field to the fluid, or the fluid maybe a magnetorheological fluid, and the device is further configured toprovide a magnetic field to the fluid.

According to other embodiments, an apparatus may be formed of one ormore of rate-dependent, elastically-deformable devices. The apparatusmay be configured as an orthotic device, safety equipment,sporting/athletic equipment, robotic assembly, strapping material, ormechanical assembly.

And, according to further embodiments, a rate-dependent,elastically-deformable device includes an elastically-deformableconfinement member; one or more filaments placed inside theelastically-deformable confinement member and having one or more plugsintegrally formed therewith that are inserted into the ends of theelastically deformable confinement member to contain the fluid; and afluid that substantially fills the remaining volume inside theelastically-deformable confinement member. Like other embodiments, theresistance force to extension of the device increases as the extensionrate of the device increases.

The one or more filaments are configured to (1) provide shear tointernal fluid, (2) seal the ends of the elastically-deformableconfinement member to prevent fluid leakage, and (3) mechanically coupleto the elastically-deformable confinement member.

The elastically-deformable confinement member can form a friction and/orinterference fit with the integrally formed plugs of the one or morefilaments. The one or more filaments having integrally formed plugs canbe formed by cutting them for a single sheet of material. For example,the sheet of material is composed of polymer, metal, rubber, fabric,fiber-reinforced polymer, or fiber-reinforced rubber. More, the one ormore filaments may further comprise an integrally formed attachmentsection, such as a loop, hook, buckle, grommet, or through-hole. The oneor more integrally formed plugs are barbed, in some implementations.

According to yet other embodiments, a rate-dependent,elastically-deformable device includes: an elastically-deformableconfinement member; one or more filaments placed inside theelastically-deformable confinement member, wherein the one or more ofthe filaments include a series of discrete positions or steps, whichsequentially engage another structure within the elastically-deformableconfinement member as the one or more filaments move; and a fluid thatsubstantially fills the remaining volume inside theelastically-deformable confinement member. Again, the resistance forceto extension of the device increases as the extension rate of the deviceincreases.

The positions or steps are configured to engage another filament and/ora fixed detent or tooth member fixed to the interior of theelastically-deformable confinement member. The positions or steps arelocated at regularly-spaced intervals, increasing or decreasingintervals, or irregular-spaced intervals on the one or more filaments.The one or more filaments may include ratcheting structure, ball andsocket means, or bristle or line comb elements to provide the series ofdiscrete positions of steps. The one or more filaments have a helical,wavy, sinusoidal, triangular wave, square wave, or sawtooth shape, forinstance.

According to further embodiments, a rate-dependent,elastically-deformable device includes: an elastically-deformableconfinement member; a pair of opposing filaments placed inside theelastically-deformable confinement member, with one end of each of thepair attached to opposite ends of the elastically-deformable confinementmember and the other end of the each of the pair unattached to theelastically-deformable confinement member; and a fluid thatsubstantially fills the remaining volume inside theelastically-deformable confinement member. In this embodiments andothers, the resistance force to extension of the device changes as theextension rate of the device changes. When the elastically-deformableconfinement member is in an undeformed state, the filaments at leastpartially can overlap one another, in some instances. In the devices,the filaments can be configured as cables or ribbons. The cablefilaments have a small cross-sectional shape (e.g., cylindrical) and arecapable of intertwining with each other, and the ribbon filaments have agenerally flat cross-sectional shape and are incapable of intertwiningwith each other. The elastically-deformable confinement member hasanisotropic properties. The elastically-deformable confinement memberhas a higher resistance to radial extension compared to its resistanceto longitudinal extension. The fluid might be a Non-Newtonian fluid,non-shear thickening fluid. These fluids may include, for example, ashear thinning, thixotropic, rheopectic, a Bingham, viscoplastic, orviscoelastic fluid.

According to additional embodiments, a rate-dependent,elastically-deformable device includes: an elastically-deformableconfinement member; one or more filaments placed inside theelastically-deformable confinement member; and a shear-thickening fluidthat substantially fills the remaining volume inside theelastically-deformable confinement member, the shear-thickening fluidcomprising a suspension of non-spherical solid particles in a liquid.The resistance force to extension of the device increases as theextension rate of the device increases. The non-spherical solidparticles might have an aspect ratio of about 2:1 or more. And theymight comprise precipitated calcium carbonate (PCC) particles, forinstance.

Further embodiments can provide apparatuses that include one or morerate-dependent, elastically-deformable devices, which mechanicallycouple a body-worn device to the body of the individual wearing theapparatus. The body-worn device might be a slip-on glove and the one ormore devices are positioned in the glove to encircle the wrist regionwhen worn by the individual and configured to be expended over the handand wrist when the individual puts on or takes off the glove. Or thebody-worn device might be a slip-on shoe or boot and the one or moredevices are positioned in the shoe or boot to encircle the ankle regionwhen worn by the individual and configured to be expended over the footand ankle when the individual puts on or takes off the shoe or boot.

These and other embodiments are further discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Thedrawings are not to scale unless so stated. It is to be noted, however,that the appended drawings illustrate only typical embodiments of thisinvention and are therefore not to be considered limiting of its scope,for the invention may admit to other equally effective embodiments.These embodiments are intended to be included within the followingdescription and protected by the accompanying claims.

FIGS. 1(a)-1(c) illustrate schematics of one rate-dependent,elastically-deformable device, and its operation, according to oneembodiment, where FIG. 1(a) shows the device at an initial, undeformedstate, FIG. 1(b) shows the device in a state during slow elongation; andFIG. 1(c) shows the device in a state during rapid elongation.

FIGS. 2(a)-2(b) illustrate experimental measurements of force versusdisplacement for one rate-dependent, elastically-deformable devicepulled at different elongation rates, demonstrating the rate-dependentresistance to extension, where FIG. 2(a) shows a plot of force versusdisplacement, and FIG. 2(b) shows a plot of force versus time, fordifferent elongation rates.

FIGS. 3(a)-3(b) illustrate two knee braces including rate-dependent,elastically-deformable devices, where FIG. 3(a) shows an elastic kneebrace with small diameter devices arrayed on the knee brace to providetargeted reinforcement, and FIG. 3 (b) shows a hinged knee brace inwhich a larger diameter device resists high rate bending.

FIGS. 4(a)-4(b) illustrate an ankle brace including rate-dependent,elastically-deformable devices, and its operation, where FIG. 4(a) showsa situation of a person walking normally over an inclined surface, andFIG. 4(b) shows a situation of a quick, abrupt drop onto an inclinedsurface.

FIGS. 5(a)-5(b) illustrate a head and neck restraint device includingrate-dependent, elastically-deformable devices, where FIG. 5(a) showsthe device coupling between the helmet and shoulder portions of aprotective vest, and FIG. 5(b) shows the device coupling between thehelmet and shoulder portions of clothing.

FIGS. 6(a)-6(e) illustrate various other rate-dependent,elastically-deformable devices embodiments, where FIG. 6(a) shows endplugs used for sealing the devices along with thin, stiff ribbons, FIG.6(b) shows compression sleeves placed on the ends of the internalfilaments to prevent puncture of the filament ends through the walls ofthe tubing, FIG. 6(c) shows a plurality of compression sleeves attachedto the filament to increase the surface area of the filament and/or toincrease fluid shearing, FIG. 6(d) shows elastic recovery componentsconnected to the end of the opposite filaments which serves to decreaserecovery time for the device to return to its initial undeformed state,and FIG. 6(e) shows an inextensible element used to limit ultimateextension of the device.

FIG. 7 illustrates an end plug of one rate-dependent,elastically-deformable device according to one embodiment.

FIG. 8 shows a rate-dependent, elastically-deformable device having anintegrated barbed ribbon filament according to further embodiments ofthe invention.

FIG. 9(a) shows one exemplary integrated barbed ribbon filament, andFIG. 9(b) shows three exemplary embodiments of the fastening sectionthereof.

FIGS. 10(a)-10(e) show exemplary devices which provide additionalmechanical locking during high rate loading according to otherembodiments. FIG. 10(a) shows a rate-dependent, elastically-deformabledevice which incorporates ratcheting filaments according to andembodiment. FIG. 10(b) is a plot of the force-displacement response ofwavy ribbon device of FIG. 10(a), showing the ratcheting effect forvarious stretching rates (in millimeters per seconds). FIG. 10(c) showsanother exemplary device with ratcheting filaments having a sawtoothconfiguration according to an embodiment. FIG. 10(d) shows anotherexemplary device with ratcheting filaments having a ball and socketconfiguration according to an embodiment. FIG. 10(e) shows anotherexemplary device having bristle or line comb elements attached to thefilaments according to an embodiment.

FIGS. 11(a)-11(c) show a rate-dependent, elastically-deformable devicehaving one or more ribbon filaments according to embodiments. FIG. 11(a)shows the device in an initial, undeformed state, whereas FIG. 11(b)shows the device in a state during low-rate elongation and FIG. 11(c)shows the device in a state during high-rate elongation.

FIG. 12(a)-12(c) show a rate-dependent, elastically-deformable devicehaving one or more cable filaments according to embodiments. FIG. 12(a)shows the device in an initial, undeformed state, whereas FIG. 12(b)shows the device in a state during low-rate elongation and FIG. 12(c)shows the device in a state during high-rate elongation.

FIG. 13(a) is a plot of response for a device having a higher modulusViton® tubing, and FIG. 13(b) is a plot of response of a device withlower modulus silicone tubing.

FIG. 14(a) is a plot of response of a device having a liquid comprisingspherical silica (in glycol) system, and FIG. 14(b) is a plot ofresponse of a device having a liquid comprising a precipitated calciumcarbonate (PCC) shear thickening fluid (STF) system.

FIG. 15 shows a glove closure incorporating a rate-dependent,elastically-deformable device according to an embodiment.

FIG. 16 shows a shoe closure incorporating a rate-dependent,elastically-deformable device according to an embodiment.

DETAILED DESCRIPTION

Rate-dependent, elastically-deformable devices according to variousembodiments can be stretched and recovered at low elongation rates. Yetthey become stiff and resistive to stretching at high elongation rates.

FIGS. 1(a)-1(c) illustrates one rate-dependent, elastically-deformabledevice 10 and its operation in accordance with one embodiment of thepresent invention. These figures show a cross-sectional cut-away viewalong the length of the device 10. In general, the rate-dependent,elastically-deformable device 10 includes an elastically-deformableconfinement member 1 which houses one or more filaments 2, as well as afluid 3 which substantially fills the remainder interior volume of theconfinement member 1. The fluid 3 is sealed within the confinementmember 1 by a crimp seal 4. The device 10 is configured to elongate orotherwise stretch by the application of an external tensile forceapplied at its ends.

The resistance force to extension of the device 1 is designed andconfigured to increase as the rate of extension or rate of elongation ofthe device 10 increases. The extension rate or elongation rate of thedevice can be expressed, for example, as a relative elongation of thedevice as a function of time or the speed/velocity of the device at oneof its ends which displaces with respect to the other. These rates maybe measured in units such as meters/sec, inches/sec, mm/sec, etc.,although the extension or elongation rate might also be expressed as adimensionless strain value (e.g., elongation of the device normalized bythe initial device length) as a function of time. This may be expressedin units of s⁻¹. Other conventions might also be used for extension orelongation rates. It should also be appreciated that the terms low-rateelongation and high-rate elongation as used herein may be relative to aparticular embodiment or application. Put another way, what may be a lowrate of elongation for one application may not be a low rate ofelongation for another application. Similarly, what may be a high rateof elongation for one application may not be a high rate of elongationfor a different application. Thus, a key feature of the innovativetechnology is the ability to judiciously tailor or otherwise configurethe elongation rate response of individual devices to any particularapplication.

FIG. 1(a) shows the device 10 in an initial undeformed state with noexternal tensile force applied. The elastically-deformable confinementmember 1 may be formed of rubber, silicone, elastomer, fluoroelastomer(such as sold under the tradename Viton®), urethane, natural latex,synthetic latex, thermoplastic elastomer, polymer, or the like, whichgenerally are elastic and resilient and capable of confining a fluidtherein. Latex may be stretchier than some of the other materials, butis also more porous to certain materials. The fluid 3 may be confined tointerior of the elastically-deformable confinement member 1 by crimps,plugs, barbs, melted (heat-crimped) ends, glues or adhesives (such asthermoplastic or thermoset resins) provided at the ends of theelastically-deformable confinement member 1.

In one embodiment, the elastically-deformable confinement member 1 maybe formed of a stretchable elastic tube. The use of an elastic tubeenables flexibility of the device 10 in multiple directions. For someapplications, the tube may have an inner diameter of about 0.01-100 mm,or more preferably 0.1-10 mm in an initial undeformed state. The tubemay generally have a circular cross-sectional shape for manyapplications, but it should be appreciated that other cross-sectionalshapes are also possible, such as rectangular, square, hexagonal, etc.

The elastically-deformable confinement member 1 might also be formedinto a planar shape, for example, formed by sealing the edges of twosheets of elastomeric materials to form an elastomeric membrane. Thiselastomeric body could be shaped like a square sheet, round membrane, orarbitrarily-shaped body. An array of filaments 2 could be enclosed inthis elastomeric body, and with the filaments aligned in parallel,orthogonally, or in any arbitrary combination of in-plane orientations.The precise shape of the body and the orientation of the filaments 2will be dictated by the application. It should be appreciated that otherstretchable configurations are also possible. For instance, the outerconfinement member 1 could be formed (or partially formed along itslength) of spiral wound or folded material which can elongate linearlywhen stretched, like a bellows, for example.

To prevent puncturing by the enclosed filaments 2, theelastically-deformable confinement member 1 may formed of a reasonablethickness whether formed of one layer or formed of multiple layers. Wiremesh or fibers might further be incorporated into the walls of theelastically-deformable confinement member 1 for this purpose. Inaddition, to enhance sliding of the filaments 2 relative to theelastically-deformable confinement member 1, interior surfaces of theelastically-deformable confinement member 1 may be further provided witha low-friction coating or layer of material, such as Teflon®.

The filaments 2 may include be formed of wire, cable, ribbon, band,thread, cord or the like, of steel, polymer, glass, carbon or otherappropriate material for this purpose. The filaments 2 may be flexibleto provide flexibility of the device 10 as well, but need not beflexible for all embodiments. The filaments 2 may be monofilament ormultifilament, twisted, untwisted or braided. In one embodiment, thefilaments are flat, flexible elements, such as ribbons. And a pair ofribbons may be provided with ones of the pair being connected toopposite ends of the elastically-deformable confinement member 1 in someinstances. The ribbons may be formed of strip-shaped materials formed ofnylon or metal, for example. There are certain advantages to using flatribbons including (i) there is more shear area between a pair ofribbons, as compared to a pair of round cables, so that higher forceresistance to elongation is possible, and (ii) ribbons can be stifferthan cables so the ribbon-based device recovers from its stretched state(i.e. relaxes) faster than a cable-based device.

In the preferred embodiment, one end of each and every filament 2 may becoupled to the elastically-deformable confinement member 1, preferablyat or near its ends. To this end, the filaments 2 may be mechanicallyand/or adhesively coupled to the confinement member 1. For mechanicalattachment, a crimp, clamp, spring clip, threaded fastener, snap-onfastener, stitch, and/or the like may be used. FIGS. 1(a)-1(c)illustrate the device 10 having filaments 2 coupled to the ends of theelastically-deformable confinement member 1 by a crimp seal 4. Foradhesive coupling, various thermosetting or thermoplastic (heat-setting)glues and adhesive may be used, including hot-melt, urethane, silicone,epoxy, acrylate, or the like, as some examples. If the filaments 2 arethemselves readily stretchable or elastic, both of their ends could becoupled to opposite ends of the elastically-deformable confinementmember 1 so as to stretch along with the elastically-deformableconfinement member 1.

In another embodiment, one or more filaments 2 in the device could beunconstrained to the confinement member 1. These filaments would befreely floating in the device, but would provide some mechanical orviscous coupling to other filaments 2 during device extension.

End effectors (not shown) may be coupled to or otherwise providemounting points on the ends of member 1 which may used to connect thedevice 10 to other systems such as mechanical linkages. Depending on theapplication, the end effector mounting may be permanent or readilyremovable. Such end effectors may include, for instance, threadedattachment (e.g., via screws or eyehooks), clips, clasps, buckles,snaps, buttons, straps, knots, stitches/stitching, staples, hookedfasteners, clamps, cotter pins, nails, glue/adhesives, or the like.

For some applications, the filaments 2 may have an outer diameter ofabout 0.01-10 mm in diameter, or more preferably 0.1-1 mm. Smaller andlarger filaments might also be used for other applications. In order toinhibit their puncturing through the outer confinement member 1, thefilaments 2, and particularly their ends, may be modified. For example,filament modifications may include rigid, smooth balls; soft coatings;filament loops; low-friction coatings; guide bushings or washers;chamfering; or compression sleeves. Grinding, sanding, or soldering mayalso be used to blunt or dull the tips the filaments 2 to inhibitpuncturing through the confinement member 1.

Generally speaking, the filaments 2 should have some degree of stiffnessfor effective operation of the device 10. For example, the filaments 2may be “push-pull” cables. By push-pull, it is meant that the filament 2can readily be pushed and pulled through the fluid 3. Most filaments aresufficient to be pulled through a fluid because the drag between thefilament and fluid tends to keep the filament in a state of tensiongenerally unfurling the filament. However, when pushed through thefluid, the viscosity of the fluid tends to keep the filament in a stateof compression. Thus, a very thin flexible thread might not be aneffective filament because it may buckle, ball-up, or tangle-up due tocompressive forces between the filament and the fluid when the deviceretracts. To increase shearing of the fluid 3, the filaments 2 mayfurther include one or more crimps, barb, ridges, waved surfaces (e.g.,square, triangular, sawtooth or sinusoidal shaped surfaces), etc. Also,the filaments 2 might be arranged in a helical (or “corkscrew”)arrangement to encourage entanglement.

One important aspect of the invention is that the resistance force toextension of the device changes, and in particular, increases as theextension rate of the device increases through the use the fluid 3. Thefluid 3 may be selected so as to change its rheological properties asthe rate of extension of the device changes. For example, the device 10may be designed so as to have a predetermined threshold rate ofextension in which such a change occurs. Thus, at low rates below thethreshold, the filaments 2 can readily slide through the fluid 3 and/orpast each other. Yet at high rates above the threshold, the fluid 3transforms to a more rigid material or higher viscosity fluid whichgreatly reduces or prevents movement of the filaments 2 through thefluid 3 and producing a stiff linear element. Put another way, thedevice 10 may be thought of as being easily stretchable at lowelongation rates, but “stiffens” or “locks up” (i.e., rigidly resists orsubstantially prevents any further deformation) when pulled quickly athigh elongation rates.

The fluid 3 substantially fills the remaining volume inside theelastically-deformable confinement member 1 once the filaments 2 areinstalled therein. The fluid 3 may be a Newtonian or non-Newtonianfluid. Newtonian fluids have a viscosity that may change withtemperature, but do not change with the strain rate. By contrast,non-Newtonian fluids have a viscosity that changes with the strain ratewhich may enable devices to be more tailored for certain operationalperformance.

In some embodiments, fluid 3 may be a shear thickening fluids (STFs).STFs, one type of non-Newtonian fluid, are materials that flow like aliquid at low deformation rates, but become highly resistant to flow athigh deformation rates. Exemplary thickening fluids which may be used inaccordance with the embodiments of the present invention are disclosedin Norman J. Wagner and John F. Brady “Shear thickening in colloidaldispersions,” Phys. Today 62, 27 (2009), herein incorporated byreference. Stretching the device 10 at low rates does not transition theSTF, and the filaments 2 are free to move through the fluid 3 and slidepast each other. If, instead, the device 10 is pulled quickly, highshear rates develop between the filaments and the STF material hardens,binding the filaments together and providing high resistance toelongation or a stiff, generally unstretchable device state. Relaxationof the force induces the STF to return to a flowable state, and thedevice once again becomes stretchable. By using a Newtonian fluid,rather than a true shear thickening fluid, one can get a usefulrate-dependent response, although the rate-dependence of the response isnot nearly as severe or drastic as devices containing an STF. The idealrate-dependent response of a device depends on the application. For someapplications, severe stiffening may be desirable to “lock” the deviceand prevent further motion. In other applications, a “locked” responsemay create an undesirably severe effect; instead, a device that is stillextensible, but at considerably higher elongation forces, might be moredesirable. The properties of fluid 3 can be tailored to provide thedesired device response.

In some embodiments, the fluid 3 may be a suspension of solid particlesin a liquid (which may also be referred to as a carrier fluid or carrierliquid). For example, the suspension may be formed of colloidalparticles generally nano-sized (i.e. 1-1000 nm). Colloidal refers to thefact that the particles are intact solid particles, they may notdissolve in the liquid, and they are generally stabilized in the liquidso that they do not agglomerate, settle, or float to the surface of theliquid system over short periods of time (i.e. they are stable for days,weeks, or longer). However, devices 10 may be constructed with a fluid 3that is a suspension of larger size solid particles (i.e. 10-1000 μm, oreven larger), which do not dissolve in the liquid and are generallystable in the liquid too. In these devices, the fluid is technically nota colloid. The term “suspension” as used herein is intended to encompassboth colloids and suspensions of larger size solid particles in aliquid.

Depending on the type of particles and liquid, and the desirednon-Newtonian response, the solid particles may constitute 10-70% byvolume of the fluid 3; more preferably, the solid particles constitute30-60% by volume of the fluid 3. For examples, a preferred volumefraction for spherical particles is around 50% by volume; a preferredvolume fraction for high aspect ratio precipitated calcium carbonateparticle may be as low as 35% The liquid could be water, oil, apolymeric liquid, a glycol, a fluorofluid, or glycerin, for example. Thecolloidal particles may be composed of ceramics, polymers (such aspoly(methyl methacrylate) (PMMA) or polystyrene), or metals. Or, theymay comprise of silica, alumina, titania, clay, precipitated calciumcarbonate, or ground calcium carbonate. It is believed that precipitatedcalcium carbonate is more likely to be stable than ground calciumcarbonate in some instances. One or more additional additives might alsobe included in the fluid 3 which function as stabilizers, emulsifiers,surfactants, pigments, etc. The fluid 3 may also include gels, gums, andputties.

In other embodiments, the fluid 3 may be an electrorheological fluid, ora magnetorheological fluid. Electrorheological fluids include asuspension of extremely fine non-conducting particles (e.g., up to 50micrometers diameter) in an electrically insulating fluid. The viscosityof these fluids can change reversibly (e.g., an order of up to 100,000)in response to an electric field. Magnetorheological fluids include asuspension of fine ferromagnetic particles in a liquid. When subjectedto a magnetic field, the fluid greatly increases its viscosity, to thepoint of becoming a viscoeleastic solid. In the case of using anelectrorheological fluid, a voltage may be applied to the fluid 3 byusing a voltage-generating device with opposite electrodes attached tofilaments at opposite ends of the device; thus creating an electricfield across the fluid 3 that would trigger a thickening response in thefluid. Similarly, in the case of using a magnetorheological fluid, amagnetic-field-generating device provided in the vicinity of the fluid 3(for example, using an electromagnet) generates a magnetic field to thefluid 3 such that the fluid 3 can increase in viscosity or transition toa non-flowable state. Suitable microcontrollers, which may include knownfeedback or feedforward control algorithms, may be further provided tocontrol the voltage-generating device and magnetic-field-generatingdevice thus providing a desired fluid response.

When the device 10 is subjected to an external tensile force, theelastically-deformable confinement member 1 elongates, and the one ormore filaments 2 are pulled or dragged through the fluid 3 as itstretches. The relevant movement of the filaments 2 through the fluid 3creates shearing flow(s) in the fluid 3. Some shearing flow may also becreated by relevant movement of the fluid 3 and the interior surface(s)of the elastically-deformable confinement member 1 and/or within thefluid 3 itself. The shearing flow of the fluid 3 creates a force withinthe device 10 which tends to resist the external tensile force that iselongating the elastically-deformable confinement member 1.

In general, the resistive force due to the shearing flow of the fluid 3is largely dependent on the speed or rate of elongation/stretching ofthe elastically-deformable confinement member 1, the surface area of thefilaments 2, and/or the spacing of the filaments 2 between one anotherand the interior surface(s) of the elastically-deformable confinementmember 1. Other factors may also influence the resistive force, such thecross-sectional shape of the elastically-deformable confinement member1, the shape of the filaments 2, and/or the viscosity of the fluid 3,for instance.

FIG. 1(a) shows the rate-dependent, elastically deformable device 10 inan undeformed state. The elastically-deformable confinement member 1here is in an initial, undeformed state.

As illustrated in FIG. 1(b), stretching the device 10 with an externaltensile force F_(LR) in an attempt to impose low-rate elongation doesnot create sufficient resistance force in the device 10, such that thefilaments 2 are free to readily be pulled through the fluid 3 and/orslide past each other. Here, the elastically-deformable confinementmember 1 has been stretched and the filaments 2 have been pulled andstraightened somewhat and slid past each other. The fluid 3 remains in aflowable state similar to that of the device 10 in its initialundeformed state. Upon gradual release of the external tensile forceF_(LR), the elastically-deformable confinement member 1 tends to returnto its initial undeformed shape and length as shown in FIG. 1(a).

On the other hand, stretching the device 10 with external tensile forceF_(HR) in an attempt to impose high-rate elongation, as illustrated inFIG. 1(c), changes the operable characteristics of theelastically-deformable device 10. For instance, if the device 10 ispulled quickly and elongates at a high rate, high shearing rates developbetween the elastically-deformable confinement member 1, the filaments 2and the fluid 3. The high shearing rates cause the fluid 3 to generate ahigh resistance force in the device 10, preventing the filaments 2 fromreadily sliding through the fluid 3 and/or past each other. Theelastically-deformable confinement member 1 has stretched a smallamount, and the filaments 2 have straightened slightly. Due to the highshearing of the fluid 3, the fluid 3 has now transformed into a morerigid-state material 3′. The filaments 2 are no longer free to readilyslide past one another. This results in the device 10 transitioning to adevice that is highly resistant to elongation, or becomes so resistantto elongation so as to become unstretchable. The device 10 will remainin the stiffened state as long as force is being applied to the ends ofthe device. If the force is relaxed, the fluid 3′ will return to aflowable state like fluid 3, and the device 10 will gradually reduce inlength back to the initial, undeformed state of the material shown inFIG. 1(a).

In some instances, the velocity of the pulling is adjusted to adjust theaction of the device 10. That is, imposing low extension-rate velocityV_(LR) or high extension-rate velocity V_(HR). This has the same effectat pulling with low rate force F_(LR) or high rate force F_(HR).

FIGS. 2(a)-2(b) show experimental force measurements during elongationof a prototype device stretched at different rates. The elongation rateswere 50 mm/min, 500 mm/min, 1,000 mm/mm, 3,000 mm/min and 5,000 mm/min.The device gage length in these experiments was 152 mm, so thesedeformation rates correspond to strain rates of 0.0055, 0.055, 0.11,0.33, and 0.55 s⁻¹, respectively. FIG. 2(a) shows a plot of force versusdisplacement, and FIG. 2(b) shows a plot of force versus time, for theseelongation rates.

The force versus displacement plot FIG. 2(a) demonstrates therate-sensitive response of the device. The liquid here was a STF whichwas formulated by blending 450-nm-diameter silica and ethylene glycol(EG) at a mass ratio of 1.92 g silica:1 g EG. The STF was dispersedusing a rolling jar mixer over a period of 24 hours. The STF was thenplaced inside a 6.35-mm-ID, 7.9375-mm-OD Viton® tube with nylon end capsand 0.794-mm-diameter stainless steel wire rope with compression sleeveson the end. The tubing was filled with shear thickening fluid bypartially clamping one end of the tubing with surgical tubing forcepswhile slowly pouring the fluid in until the fluid reached the surgicalforceps. In some cases, it was helpful to apply low amounts of heatusing a heat gun or to inject the fluid using a 3-mL syringe. Thesurgical forceps were removed and then the tubing was plugged at one endusing the nylon plugs with attached wires described above. At thispoint, the tube was gently massaged to push air bubbles to the top ofthe tube and more fluid was added in order to fill the void spacepreviously occupied by the air bubbles. Afterwards, the second nylonplug was inserted into the tubing.

The force versus time plot FIG. 2(b) shows that the devices respond veryrapidly, with the high rate plateau force reached in less than 100 msafter force application. This rapid response means that there would bevery little lag time between application of high elongation rate, andtransformation of the device to a more resistive state.

As apparent, at the low elongation rates, the device provides verylittle resistance to stretching. One the other hand, as elongation rateincreases, the resistance to deformation (force values during extension)increases. Comparing the highest rate response to the lowest rateresponse at 100 ms, the resistive force at high rate is approximately100× higher than the resistive force at low rate. These particularembodiments of the device show a resistive force that peaks and thenplateaus, which could be a beneficial feature of a device. For example,the long plateau force indicates high energy absorption duringelongation. Also note that if the device is elongated at high rates, butthe available elongation force is less than the plateau force, thedevice would essentially feel unstretchable and provide a rigidresponse. Other devices can be engineered with considerably higherresistive forces, and resistive forces that do not plateau but reach alimiting displacement beyond which further elongation would requireexceedingly high forces.

The device tested was designed to provide much higher resistance toelongation as the elongation rate increases. But it was not designed torigidly lock-up at high rates of elongation (rather, some elongationcontinued at higher rates of elongation just at much higher force). Thedevice nonetheless still appeared to lock-up if the rapidly appliedforce is less than the plateau force, such as during impulse loading.While rigid locking-up of the device may be useful for someapplications, for other applications a rigid locking effect would be toosevere a response, and a higher elongation force is a preferredresponse.

According to various embodiments of the present invention, one or morerate-dependent, elastically-deformable devices may be incorporated intovarious devices and apparatuses to provide rate-dependent operationalperformance. For example, in some embodiments, one or morerate-dependent, elastically-deformable devices may be incorporated intoan apparatus such as an orthotic device to create rate dependent braces.Exemplary orthotic devices which may be benefited in the manner mayinclude, for example, head and helmet braces, knee braces, ankle braces,back braces, neck braces, wrist braces, slings, and other orthoticdevices. The rate-dependent, elastically-deformable devices may also beprovided in other wearable equipment, such as shoes, boots, headgear,belts, harnesses, or the like. This technology presents a new approachand, thus orthotic devices that can provide higher resistance to motionduring higher speed events which a soldier or athlete may encounter.These new and improved devices will be more effective at resistingunplanned loads and preventing injuries. Many joint injuries associatedwith rapid twisting and translations of limbs and joints, such asslipping, stepping in a hole, landing from a jump, or planting a footwhile changing direction may be prevented. In other embodiments, one ormore rate-dependent, elastically-deformable devices may be incorporatedinto safety equipment, sporting/athletic equipment and goods, robotics,restraints (e.g., seat-belts) and mechanical assemblies. According,various applications, such as, linkages, vehicle suspension systems,robotics, “strapping” (e.g., bungee-type cords, self-tightening straps,etc.) clothing and woven textiles may be benefited. One device might beused as a replacement for a simple Velcro® or an elastic strap.

FIGS. 3-5 show examples of various orthotic devices according toembodiments of the present invention. In FIGS. 3(a)-3(b), the orthoticdevices are knee braces which are configured to be worn on a person'sleg 50 on the knee 55 to provide increase support and/or stability forthe knee 55. The precise number of elongational devices 10 that areincorporated into the knee braces, and the orientation of these devicesrelative to knee physiology or desired kinesiology for a given activityor injury risk, could be tailored to a particular application. The kneebraces are designed to permit normal walking and other activities, butstiffen and resist deformation during high rate events, like landingfrom a jump. Moreover, the knee braces provide rate-dependentoperational performance not found in conventional braces.

FIG. 3(a) shows an elastic knee brace 100 according to one embodiment.The knee brace 100 includes multiple rate-dependent,elastically-deformable devices 10 that are fastened to, bonded to, woveninto, and/or otherwise attached to the body 102 of the knee brace 100.The body 102 may be formed of a conventional elastic fabric textile,such as sold under the tradename Spandex®. Or the body 102 may be formedof a rigid or semi-rigid material which comports to the curvature of theleg 50 or knee 55 as generally known. When worn, the body 102 snuglyengages the leg 50 and knee 55 and holds the knee brace 100 in place.Adjustment straps (not shown) having buckles or hook and loop type(e.g., Velcro®) fastening may be further included to better couple thebrace 100 to the leg 50 and knee 55. To facilitate incorporation intothe fabric of the body 102, the devices 10 may have a small outerdiameter, such as 0.1-10 mm.

FIG. 3(b) shows a hinged knee brace 200 according to another embodiment.The knee brace 200 body includes an upper portion 202 worn above theknee 55 and a lower portion 204 worn below the knee 55. The upper andlower portions 202, 204 are coupled with a pivot 206 to provide hingedmovement of the brace 200 at the knee 55.

The upper and lower portions 202, 204 may be formed of a conventionalelastic fabric textile. Or they may be formed of a rigid or semi-rigidmaterial which comports to the curvature of the leg 50 and knee 55 asgenerally known. When worn, the upper and lower portions 202, 204 of thebrace 200 snugly engage the knee 55 and holds the knee brace 200 inplace on the person's leg 50. Adjustment straps (not shown) havingbuckles or hook and loop type (e.g., Velcro®) fastening may be furtherincluded to better couple the brace 200 to the leg 50 and knee 55.

The knee brace 200 further include one or more rate-dependent,elastically-deformable devices 10 which couple to the upper and lowerportions 202, 204 of the brace 200. As shown, one rate-dependent,elastically-deformable device 10 externally couples those elementsbehind in the rear of the knee 55. Because of the greater forces thedevice 10 may be subject to in this orientation, it may have a largediameter, such as 1-20 mm. The device(s) 10 stretches freely duringnormal motion of the hinged knee brace 200, but becomes rigid duringhigh rate motions that may cause injury.

The lengths, positions, number, orientations and/or operationalcharacteristics of the devices 10 in the knee braces 100 and 200 arestrategically designed to provide optimal support. The devices 10incorporated into the braces 100 or 200 may have differentcharacteristics. As shown in FIGS. 3(a) and 3(b), the rate-dependent,elastically-deformable device(s) 10 may be positioned in a generallyparallel orientation parallel to the length of the leg 50 in both ofthese knee brace embodiments. However, the devices 10 may beadditionally or alternatively oriented generally orthogonally to thelength of the leg 50, and/or at some angle thereto. Also, the devices 10might further be oriented in a “criss-cross shape” or “X-shape” toprovide greater lateral support to the knee 55. Other configurations arealso possible. Under normal walking conditions, the elements of thedevices 10 deform passively and do not resist motion. Under high loadingrate, potentially injurious conditions, such as a knee hyperextension orknee twist during slippage, the devices become rigid and greatly limitor preferably prevent further motion of the knee 55.

FIGS. 4(a)-4(b) show an ankle brace 300 and its operation, according toan embodiment. The ankle brace 300 includes multiple rate-dependent,elastically-deformable devices 10 that are fastened to, bonded to, woveninto, and/or otherwise attached to the body 302 of the brace 300.

The body 302 may be formed of a conventional elastic fabric textile. Orthe body 302 may be formed of rigid or semi-rigid material whichcomports to the curvature of the leg 50, foot 52 or ankle 54 asgenerally known. When worn, the body 302 snugly engages the leg 50, foot52 and ankle 54 and holds the ankle brace 300 in place. Adjustmentstraps (not shown) having buckles or hook and loop type (e.g., Velcro®)fastening may be further included to better couple the brace 300 to theleg 50, foot 52 and ankle 54. These devices 10 enable low rate extensionbut prevent higher rates of extension and rotation of the ankle brace300.

FIG. 4(a) shows a situation of a person walking normally over aninclined surface I. In this situation, the person's foot 52 (on theleft) needs to rotate slightly with respect to the person's leg 50 fortraction and balance. In this situation, the ankle brace 300 isconfigured to permit a low rate of inversion of the ankle 54 and foot 52which is typically expected for walking. During the normal gait cycle,the foot both pronates and supinates. Pronation is a combination ofthree ankle movements, abduction, eversion, and dorsiflexion, whilesupination is combination of adduction, inversion, and planar flexion.When the foot hits the ground, the ankle pronates to absorb the shock,and when it pushes off, the ankle supinates.

FIG. 4(b) shows a situation of a quick, abrupt drop onto an inclinedsurface I. It is noted that alike elements to those in FIG. 4(a) areshown here, and will be referenced. Typically, in this situation, theperson is not expecting this drop. This may occur for example when oneinadvertently steps off a curb. And, because the person is not expectingthe drop, the high rate of ankle inversion associated with the landingonto the incline surface I ordinarily (without the aid of the anklebrace 300) may cause injury to the person, such as an ankle sprain, orworse yet, possibly a break. It is noted that 70-80% of typical anklesprains are caused by ankle inversion, whereas a smaller percentage iscaused by ankle eversion. But, by wearing ankle brace 300, the anklebrace 300 advantageously resists the high rate of ankle inversion toreduce injury in this situation.

FIGS. 5(a)-5(b) show a head and neck restraint device 400 according toan embodiment. The person 500 shown here may be a soldier or warfighterwearing military equipment, such clothing 15, a helmet 20, a facemask 25(e.g., having goggles and face guard), and protective vest 30 (shown inFIG. 5(a) only).

The head and neck restraint device 400 couples between to person's headand shoulders. As shown in FIG. 5(a), the device 400 couples between thehelmet 20 and shoulder portions of the protective vest 30 via mountingpoints 35. Or, as shown in FIG. 5(b), head and neck restraint device400′ couples between the helmet 20 and shoulder portions of the clothing15 via mounting points 35. The mounting points 35 may include clips,clasps, buckles, snaps, buttons, straps, knots, stitches, hookedfasteners, clamps, or other end effectors, for example. The device 400further includes one or more rate-dependent, elastically-deformabledevice(s) 10. A pair of devices 10 is shown in the figures herepositioned axially, one on each side of the person's head. This designis not to be considered limiting; other embodiments can be envisionedthat use more devices, different orientations, and different fixturing.For instance, multiple devices 10 might be positioned axially around theentire neck in an orthotic device similar to a neck brace. Also, one ormore devices 10 may be provided in a radial orientation, additionally oralternatively, to resist head turning or lifting motion at high ratesalso.

During normal operation, the devices 10 are free to stretch and do notresist head motion. Under high rate events, such as a blast event or asecondary impact when a soldier is thrown into a wall or vehicleinterior, the devices 10 become stiff and resist extension. Under thelatter conditions, loads to the helmet 20 are transmitted directly tothe shoulders, rather than to the head and neck. By reducing head andneck loads, the risk of injury is significantly reduced. A similar head-and neck-protective device is further envisioned for contact sportsapplications, such as for football, hockey or lacrosse helmets in orderto reduce the likelihood of concussions during impact.

FIGS. 6(a)-(e) show rate-dependent, elastically-deformable device(s) 10′according to other embodiments of the invention. These figures show across-sectional cut-away view along the length of the device(s) 10′. Thedevice(s) 10′ here are shown in their initial undeformed state, but areconfigured to elongate or otherwise stretch by the application of anexternal tensile force through their ends, similarly to as shown inFIGS. 1(a)-1(c).

As shown in FIG. 6(a), the rate-dependent, elastically-deformable device10′ includes an elastically-deformable confinement member 1′ whichhouses one or more filaments 2′, as well as a fluid 3 whichsubstantially fills the remainder interior volume of the confinementmember 1′. Filaments 2′ may be formed of are flexible, flat, stifffilaments, such as nylon ribbons. They may have a rectangularcross-section in some embodiments. To confine fluid 3′ inside theelastically-deformable confinement member 1′, plugs 5 may be used. Theelastically-deformable confinement member 1′ may be formed of tubing mayhave overall length of about 6-in and an outer diameter of about5/16-in. The filaments 2′ may have a length of 4.75-in. The plug 5 mayhave a diameter of about 0.3175-in to provide a frictional orinterference fit with the confinement material tubing 1′. The plugs 5seal the ends of outer confinement member 1 so as to maintain the liquid3 therein. Preferably, this is a hermetic seal to prevent evaporationand/or outgassing, as well as prevent the ingress and egress of dirt,debris, moisture, and contaminants which could contaminate the liquid 3′and impede operation of the device 10′. The plugs 5 also may serve as anattachment point for the filaments 2′; for example, the plugs may behollow in the barbed section, so that one end of the filament can beplaced in the hollow section, then adhesive can be poured into the plugto permanently attach the filament end to the nylon plug. Furthermore,the outside end of the plug 5 provides a convenient mounting orattachment point for other hardware (e.g., end effectors) for couplingthe device 10 to other bodies.

FIG. 6(b) shows compression sleeves 6 placed on the ends of the internalfilaments to prevent puncture of the filament 2′ ends through the wallsof the tubing 1′. FIG. 6(c) shows a plurality of compression sleeves 6placed not only at the ends but along the length of the filaments 2′ toincrease the surface area of the filament 2′ and/or to increase shearingof the fluid 3′. FIG. 6(d) shows elastic recovery components 7 connectedto the end of the opposite filaments 2′, which serves to decreaserecovery time for the device 10′ to return to its initial undeformedstate. The elastic recovery components 7 may be springs or elasticfilaments, for example.

FIG. 6(e) shows an inextensible rigid filament 8 used to limit ultimateextension of the device (i.e. to serve as a “hard stop”). The ends ofthe hard stop 8 may be attached to the plug 5 at location 9 by adhesive,for example.

FIG. 7 shows a modified embodiment of the plug 5′ illustrated in FIGS.6(a)-6(e). The plug 5′ may include a central body portion 5 a, atapering enlarged diameter front portion 5 b, and reared flange portion5 c. The front portion 5 b, also known as a barbed portion, is adaptedto be inserted into the ends of the elastically-deformable confinementmember 1′ to confine fluid 3 therein. The enlarged diameter beingslightly larger than that of the elastically-deformable confinementmember 1′ may facilitate a friction or interference fit, for instance.Glue or adhesive may be further provided to additionally couple the plug5′ to the elastically-deformable confinement member 1′. In someinstances, the central body portion 5 a may include “flats” on itsexterior sidewalls to resist or limit rotational movement of the plug 5′when it is inserted into the elastically-deformable confinement member1′. An axial bore 5 d is provided through the body portion 5 a of theplug. The diameter of the bore 5 d in front of the flanged front portion5 c is slightly larger than the diameter of the head 11 b of thethreaded fastener 11. However, the diameter of the bore 5 d through theflanged portion 5 c is slightly larger than the diameter of the threadedportion 11 a, but slightly less than the diameter of the head 11 b. Assuch, the threaded portion 11 a of the fastener can be inserted into theaxial bore from the front side to the rear side, with the head of thefastener engaging an inner wall of the bore 5 d at the flange where thediameter of the bore changes. The nut 12 can be threaded onto thethreaded portions 11 a of the threaded fastener from the rear of theplug so as to trap and fix the threaded fastener 11 to the plug 5′.

FIG. 8 shows a rate-dependent, elastically-deformable device 10″ havingan integrated barbed ribbon filament 2″ according to further embodimentsof the invention. Here, the integrated barbed ribbon filament 2″ is usedto both seal ends of the elastically-deformable confinement member 1 andprovide internal shearing of the liquid 3 in the device. The barbed endalso serves the important role of mechanically coupling the ribbonfilament 2″ to the elastically-deformable confinement member 1. Themechanical attachment of the filaments 2″ to the elastically-deformableconfinement member 1 may be a friction and/or inference fit (e.g., withends of member 1 expanding over the ends of integrated barbed ribbonfilament 2″). The liquid 3 is contained in the elastically-deformableconfinement member 1 by the integrated barbed ribbon filament 2″ itself.To further prevent leakage of the liquid 3, the attachment may be aidedby adhesively bonding with suitable sealant, glue, or adhesive 13, forexample.

This structure offers a number of performance and manufacturingadvantages relative to the previous embodiments which includes atwo-part barbed fitting 5 with filament 2 structure (see, e.g., FIGS. 6and 7). For instance, because no adhesive bond is needed to join thefilament and plug, so there is no risk of adhesive failure at thatjunction. Also, this eliminates a time-consuming manufacturing step,i.e., gluing the plug to the filament, thus, making manufacturingquicker and easier. The overall device form factor is flatter, whichmakes it more straightforward to integrate for many strap applicationsand especially clothing and body-worn applications.

The integral barb and filament structure 2″ can be cut from a singlesheet of material using a variety of techniques, such as laser cuttingand water-jet cutting, which are rapid and low cost. Using sheet-cuttingtechniques such as laser-cutting or water-jet cutting enables low-cost,detailed control over the ribbon thickness, ribbon length, barbgeometry, etc. (rather than having to rely on off-the-shelfinjection-molded plugs).

FIG. 9(a) shows one exemplary integrated barbed ribbon filament 2″. Itincludes an attachment section 2″a, barbed section 2″b, and main ribbonsection 2″c. The structure 2″ may also integrate fastening section 2″dshown at the attachment section 2″a which aids in mechanical fasteningto other components. The thickness, width, and length of one particularfilament structure 2″, as well as the details of the barbed section 2″bgeometry, are shown. This particular embodiment is configured for adevice enclosed within a 15-cm-long piece of Viton tubing with 6.36 mmID and 7.94 mm OD. These dimensions should be considered exemplary only,and are not limiting; all dimensions can vary depending on the size,length, and desired performance of the device.

The integrated barbed ribbon filament 2″ can be cut from a single pieceof plastic sheeting, such as Nylon sheeting, with a thickness of 1.5 mm.The attachment section 2″a shown is 25 mm long by 15 mm wide, provides aregion for end effectors, clamps, or other means of connecting to otherbodies. The main ribbon section 2″c could have a width of 5 mm and alength of 10 cm. This section 2″c transitions to the barbed section 2″bwith a total width of around 15 mm, with a barb length of 10 mm. Tocomplete the barb section 2″b, the ribbon width reduces to around 10 mmfor a length of around 8 mm, providing a corner on the trailing edge ofthe barb to dig into the tubing and lock the tubing in place. Threeembodiments of the fastening section 2″d are further shown in FIG. 9(b)which comprise one or more through-holes 2″d′, buckle structure 2″d″, orgrommet 2″d′″, for example. Of course, various other geometric features,or other end effectors integrated into the attachment section 2″a formechanical fastening to other components may be used for the fasteningsection 2″d than the ones depicted here.

FIGS. 10(a)-10(e) show exemplary devices which providing additionalmechanical locking during high rate loading according to otherembodiments. FIG. 10(a) shows a rate-dependent, elastically-deformabledevice 10″′a which incorporates ratcheting means according to anembodiment. More particularly, the device 10′″a has one or moreratcheting filaments 2′ placed inside the elastically-deformableconfinement member 1. Two are shown. These ratcheting filaments 2′″include a series of discrete positions or steps, which sequentiallyengage another structure within the elastically-deformable confinementmember as the one or more filaments move to provide the “ratcheting”effect. These positions or steps are configured to engage anotherstructure within the elastically-deformable confinement member, such asanother ratcheting filament 2′″ and/or a detent or tooth member (notshown). As shown, a pair of opposing ratcheting filaments 2′″a withdiscrete positions or steps can engage one other as they move inopposing direction. More particularly, these ratcheting filaments 2′″ahave wavy or “zig-zag” features which need to displace outward so as toslide past each other to the next position or step thus creating outwardnormal force. Alternatively or additionally, the inner surface of theconfinement member 1 could include a fixed or attached tooth or detentwhich engages a filament's discrete positions or steps.

This behavior is analogous to a strap with multiple discrete adjustmentpositions, such as a strap with a series of holes that interfaces with abuckle. Unlike a conventional buckle, which requires significant manualmanipulation to readjust, the ratcheting effect of the device with awavy ribbon allows readjustment simply by pulling on the strap. Thisfeature could be useful for strap applications, as the straps tend tosettle into a series of discrete positions or “steps,” and requirehigher force to move from one position to the next.

The positions or steps could be equally-spaced apart at regularintervals, for instance, as illustrated in FIG. 10(a). Also, the spacingthere between could be configured to increase or decrease in anon-linear manner, such as an exponential, or irregular pattern. Thisprovides the designer with various tailored options for ratchetingbehavior.

FIG. 10(b) is a plot of the force-displacement response of wavy ribbondevice 10′″a of FIG. 10(a), showing the ratcheting effect for variousstretching rates (in millimeters per seconds). As the rates increase,the force necessary to effect displacement greatly increases which isconsistent with the increased shearing of liquid 3. Additionally, theratcheting effects can be appreciated in the displacements for allrates.

FIG. 10(c) shows another exemplary ratcheting filament device 10′″bhaving a sawtooth configuration according to an embodiment. The sawtoothconfiguration has a particular utility in that it can be designed toexhibit directionally-dependent resistance; for example, a pair ofsawtooth configured filaments 2′″b properly oriented results in a devicethat exhibits considerably more resistance during extension than duringcompression and relaxation. This is a special geometry because, unlikethe wave, triangular, sinusoid geometries, a sawtooth hasdirectionality, i.e., flat butt-faces engage in one direction (verybinding), inclined faces engage in another direction (easier to slidepast). For most device embodiments, high resistance in tension is ofprimary importance, but having low resistance in compression isnonetheless advantageous so that they can quickly relax.

FIG. 10(d) shows another exemplary ratcheting filament device 10′″chaving a ball and socket configuration according to an embodiment. Afilament 21 having one or more ball members 22 is connected to one ofthe ends plug. The ratcheting filaments 2′″c must spread to allow theballs 22 to be pulled-through. The liquid 3 will be highly resistant tothese outward normal forces. Here, both ratcheting filaments 2′″c areshown attached to the same end plug (or the right) and the filament 21is shown attached to the other end plug (or the left). In otherimplementations, the ratcheting filaments 2′″c might be attached todifferent end plugs.

FIG. 10(e) shows another exemplary ratcheting filament device 10′″dhaving bristle or line comb elements 23 attached to the filaments 2′″daccording to an embodiment. The comb elements 23 need to displaceoutward so that the filaments 2′″d can slide past each other. They canbe oriented so have more resistance to extension, less resistance toretraction for instance. The comb elements 23 generally should beslightly flexible or very flexible.

FIGS. 11(a)-11(c) show a rate-dependent, elastically-deformable device10″ having one or more ribbon filaments 2″″ according to embodiments.FIG. 11(a) shows the device 10″″ in an initial, undeformed state,whereas FIG. 11(b) shows the device in a state during low-rateelongation and FIG. 11(c) shows the device in a state during high-rateelongation.

One end of each of the flat ribbon filaments 2″″ is attached to oppositeends of the elastically-deformable confinement member 1 (via plugs 5)and the other end of the each of the pair is unattached to theelastically-deformable confinement member 1. The ribbons filaments 2″″have a generally flat, two-dimensional cross-sectional shape facing eachother. In this arrangement, when the elastically-deformable confinementmember 1 is in an undeformed state (FIG. 11(a)), the ribbon filaments 2′at least partially overlap one another and may continue to overlap asthey are drawn away from one another as further illustrated in FIGS.11(b) and 11(c). It has been found that flat ribbon-based filaments havea number of advantages for some applications, most notably, they simplywork more consistently and predictably because the ribbons have aconsistent configuration (i.e., they unlikely not to get intertwinedwith one another).

FIG. 12(a)-12(c) show a rate-dependent, elastically-deformable device10″″′ having one or more cable filaments 2″″′ according to embodiments.The cable filaments 2″″′ are long and thin elements. They can becylindrical in cross-section with a diameter of approximately 0.001-10mm, for example. FIG. 12(a) shows the device 10″″′ in an initial,undeformed state, whereas FIG. 12(b) shows the device in a state duringlow-rate elongation and FIG. 12(c) shows the device in a state duringhigh-rate elongation.

In contrast to the ribbon filaments 2″″ (see FIG. 11), the cablefilaments 2′″″ have a different response depending on how “intertwined”they are (i.e., the degree of which the filaments twist upon and aroundeach other) creating a more complex entanglement than would be possiblefor straight and parallel filaments. This could resemble a helicalentanglement, for instance. A concern with intertwined filaments is thatthere are multiple configuration options that can lead to slightlydifferent responses for the same device, and these configurations canvary during multiple operation cycles of a given device leading to minorinconsistencies in device response. However, the intertwining of thecables provides an opportunity for a stronger locking effect compared toflat ribbons. Flat ribbons cannot readily entangle, so the peakresistance of a flat ribbon device can be limited by factors such asslip of the enclosed liquid 3 relative to the ribbon. For a cabledevice, the cables can intertwine and, if the liquid (e.g., a STF)prevents the cables from disentangling, can create a very highresistance force even if cable-to-liquid slip is possible. For thesereasons, cable-based devices provide unique features relative to flatribbon designs, and may prove advantageous for some applications orgeometries.

One material which may be used for the elastically-deformableconfinement member 1 is a stretchable tubing material. Typical soft,high elongation tubing materials like Viton or silicone have Young'smoduli of 1-10 MPa in both the longitudinal and hoop directions. (Viton®is a well-known brand of synthetic rubber and fluoropolymer elastomertrademarked by DuPont Performance Elastomers LLC.). It has been foundthat the peak forces in the silicone tubing STF devices areapproximately 50% lower than STF devices constructed with Viton tubing.

FIG. 13(a) is a plot of response of a STF device with higher modulusViton® tubing, and FIG. 13(b) is a plot of response of a STF device withlower modulus silicone tubing. Both devices use identical filamentribbons and STF fluid. This data shows that silicone tubing is morecompliant than the Viton tubing but, since the elastic tubing forces arefar less than the peak STF device extensional resistance, the complianceof the tubing is not directly responsible for the observed differencesin device peak force. Instead, the more rigid Viton tubing may providehigher confinement, and therefore normal forces, on the enclosed STF.These increased normal forces are known to induce increases in shearresistance for STFs and dense granular media. It is possible that anideal tubing material would be anisotropic, with low resistance tolongitudinal elongation and high resistance to radial expansion tomaximize the transitional effects in the STF. Thus, according toembodiments, the confinement member may be designed or selected to haveanisotropic properties. For instance, the confinement member may havehigh compliance in the longitudinal direction, and low compliance(stiffness) in the radial or hoop direction. Or put a different way, theelastic confinement member has a higher resistance to radial or hoopextension compared to its resistance to longitudinal extension.

One anisotropic tubing material could have a ratio of hoop Young'smodulus to longitudinal Young's modulus of, for example, 10× or 100×.For example, if the longitudinal Young's modulus is 10 MPa, then thepreferred hoop direction modulus would be 100-1000 MPa. Higher hoopmoduli could be achieved by embedded, hoop-oriented fibers; a wrap offiber reinforcement, with the fibers preferentially oriented in the hoopdirection; or a confinement body, such as a spiral wound metal wire ordiscrete rings of metal or hard plastic.

The embodiments thus far have described rate-dependent,elastically-deformable devices containing a fluid, with special interestin Newtonian and non-Newtonian fluids, and more particularly,non-Newtonian fluids that are shear thickening. Non-Newtonian fluiddevices which are not shear thickening fluids may also be considered inother embodiments. Examples of these fluids include shear thinning,thixotropic, rheopectic, a Bingham fluid, viscoplastic, or viscoelastic.

Depending on the particular fluid 3 incorporated in the rate-dependent,elastically-deformable devices 10, their resistance force to extensionof the device 10 changes as the extension rate of the device increases.Indeed, the resistance force to extension can “change”— i.e., toincrease, decrease, and/or suddenly yield—as the extension rate of thedevice 10 increases. Heretofore, the disclosed embodiments, havegenerally been configured such that the resistance force to extension ofthe device “increases” as the extension rate of the device increases.But, other changes to their rate resistance are also contemplated.

For example, whereas an elastically-deformable device hosting a typicalshear thickening fluid exhibits an increase in resistance force toextension as the extension rate of the device increases, for a devicehosting other non-Newtonian fluids the resistance force to extensionwould exhibit different and potentially useful behaviors as theextension rate of the device increases. Example behaviors include aresistance force that decreases gradually as extension rate of thedevice increases, or decreases suddenly at a critical extension rate.Considering one specific example, a Bingham fluid behaves like a solidmaterial up until a certain stress level, then above a critical “yieldstress” converts into a flowable liquid. Upon relaxation of the stress,the fluid converts back to a solid-like material. The effect is observedin a material like ketchup, which will hold shape but then will flow ifacted upon by stress. A rate-dependent, elastically-deformable devicehosting a Bingham fluid would show resistance to force up until acritical internal stress was exceeded, and then would yield and extendwith little resistance. This type of device could be used, for example,as a “soft fail” connector in a more complex structure to control theprogression of damage and limit damage in critical regions, analogous tothe crush zone in an automobile. (An example would be a seat belt in amilitary vehicle, designed to hold the wearer close to the seat duringnormal off-terrain action, but would yield during a high rate underbodyexplosion to provide higher extension and more gradual body loads).Alternatively, the “soft fail” of the tether could be used to driveloads from the primary seat belt into a parallel, secondary seat beltthat is normally slack during routine use. Another example would be agarment application, where this device could act as a garment closure(for example, a wrist closure on a glove) that holds the garment on thebody during normal motion, but stretches when pulled suddenly for easydoffing and donning of the garment.

The disclosed embodiments thus far have generally been shown stretchingand thus in tension. This motion is envisioned as a more typicaloperation for most device applications. However, devices 10 should alsobe adaptable for compression situations in which the devices, do notstretch, but actually decrease or shrink in size with compressive forceor velocity. Such compression embodiments of the invention alsocontemplated, in which the resistance force to compression of the devicechanges the compression rate of the device increases.

According to yet further embodiments, the shear-thickening fluid maycomprise a suspension of non-spherical solid particles in a liquid. Thenon-spherical solid particles may comprise precipitated calciumcarbonate (PCC) particles having an aspect ratio of 2:1 or more. Theinventors investigated devices in which the STFs comprise water with 2:1aspect ratio precipitated calcium carbonate (PCC) particles. The sourcematerial is a water-based precipitated calcium carbonate slurry fromSpecialty Minerals (Bethlehem, Pa.) called “Albaglos S,” having a meanparticle size of 600 nm. (This research was reported in the journalarticle by the inventors P. T. Nenno and E. D. Wetzel. “Design andproperties of a rate-dependent ‘dynamic ligament’ containing shearthickening fluid.” Smart Materials and Structures. v23 n125019 p 1-10.30 Oct. 2014, which was incorporated in and formed a basis of theaforementioned '689 prov. application).

The plots of FIG. 14 compare the device response for the sphericalsilica (in glycol) system (FIG. 14(a) and the PCC STF system (FIG.14(b). The PCC system shows higher forces at high speeds, and a moredrastic transitional behavior from low speed to high speed response. Thedriving mechanism for the particle shape effect is that elongatedparticles tend to tumble during shear flow. This tumbling allowsparticles to interfere and collide at lower volume fractions than wouldbe necessary for a spherical system, so PCC STFs can be formulated withlower nominal (low strain rate) viscosities than spherical particleSTFs. These lower volume fractions and viscosities result in less deviceresistance at low speeds, and also result in a slight increase in thecritical shear rate necessary to achieve shear thickening. Moreimportantly, the tumbling action of these particles are believed toinduce outward normal stresses perpendicular to the shear direction. Forrate-dependent, elastically-deformable devices, the elastic confinementmember necessarily decreases in diameter during extension. The fact thatthe PCC STF is pushing outward in opposition to the contraction of theconfinement member is believed to create a compaction force that clampsonto the ribbons and increases resistance force during extension.

Another important category of application for the STF devices is strapsand closures for body-worn devices, which require some amount oflow-speed “give” for comfort, as well as conformability to complexgeometries. Body-worn systems that require a tight fit for good functionbut still need compliance for comfort are preferred applications for ourdevices. Examples include prostheses, braces, body armor, chest plates,protective athletic padding, helmet chin straps and suspension systems,glove closures, and shoe closures.

For glove and shoe closures, in particular, rate-dependent,elastically-deformable device(s) placed at the wrist or ankle locations(respectively) could allow for self-adjusting, “slip-on” gloves andshoes/boots that can be slowly stretched to pass over the foot and hand,but then contract onto the ankle or wrist to achieve a tight comfortablefit. For instance, these applications may make use of a device having apair of opposing filaments. Although, it will be appreciated that thesecan use the any of the various embodiments of rate-responsive,stretchable devices.

FIG. 15 shows a glove closure 1500 incorporating a rate-dependent,elastically-deformable device 10 according to an embodiment. The gloveportion may be conventional. The rate-dependent, elastically-deformabledevice is positioned in the glove at the wearer's wrist location. In itsinitial position, the device keeps the diameter of glove at the wristrelatively small. It must be stretched slowly to increase the diameterto slip over the wearer's wrist. Once the glove is slipped over thewearer's wrist, the device relaxes and reduces the diameter of the gloveto snugly close around the wearer's wrist. If the wearer slowly pullsthe glove off, the device will permit the wrist portion to expand indiameter to slip around the wearer's wrist. On the other hand, if theglove is pulled too fast, the device will not enable to the glove toexpand in this manner.

FIG. 16 shows a shoe closure 1600 incorporating a rate-dependent,elastically-deformable device 10 according to an embodiment. Therate-dependent, elastically-deformable device is positioned in the shoeat the wearer's ankle location. Like the glove, the device permits theshoe to be easily slipped over or off the wearer's ankle. But, if pulledtoo fast, it will not easily be removed.

These closures would resist sudden forces to hold the shoe or glove inplace during action such as sports or combat, but would slowly conformto the body to provide comfort, and could be slowly stretched to openthe closure for removal. In these applications, our device would permita shoe to be designed without conventional strap closures such ashook-and-loop (Velcro-type) fasteners or laces.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the present disclosure and its practical applications, tothereby enable others skilled in the art to best utilize the inventionand various embodiments with various modifications as may be suited tothe particular use contemplated.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

We claim:
 1. A rate-dependent, elastically-deformable device comprising:an elastically-deformable confinement member; one or more filamentsplaced inside the elastically-deformable confinement member and havingone or more barbed plugs that are inserted into the ends of theelastically-deformable confinement member to contain the fluid; and afluid that substantially fills the remaining volume inside theelastically-deformable confinement member, wherein the resistance forceto extension of the device increases as the extension rate of the deviceincreases.
 2. The device of claim 1, wherein the elastically-deformableconfinement member forms a friction and/or interference fit with thebarbed plugs.
 3. The device of claim 1, wherein the one or morefilaments and barbed plugs are formed by cutting them for a single sheetof material.
 4. The device of claim 3, wherein the sheet of material iscomposed of polymer, metal, rubber, fabric, fiber-reinforced polymer, orfiber-reinforced rubber.
 5. The device of claim 1, wherein the one ormore filaments further comprise an integrally formed attachment section.6. The device of claim 5, wherein the integrally formed attachmentsection comprises a loop, hook, buckle, grommet, or through-hole.
 7. Thedevice of claim 1, wherein the one or more barbed plugs are integrallyformed with the one or more filaments.
 8. The device of claim 1, whereinthe one or more filaments are configured to (1) provide shear tointernal fluid, (2) seal the ends of the elastically-deformableconfinement member to prevent fluid leakage, and (3) mechanically coupleto the elastically-deformable confinement member.
 9. A rate-dependent,elastically-deformable device comprising: an elastically-deformableconfinement member; one or more filaments placed inside theelastically-deformable confinement member, wherein the one or more ofthe filaments include a series of discrete positions or steps, whichsequentially engage another structure within the elastically-deformableconfinement member as the one or more filaments move; and a fluid thatsubstantially fills the remaining volume inside theelastically-deformable confinement member, wherein the resistance forceto extension of the device increases as the extension rate of the deviceincreases.
 10. The device of claim 9, the positions or steps areconfigured to engage another filament and/or a fixed detent or toothmember fixed to the interior of the elastically-deformable confinementmember.
 11. The device of claim 9, wherein the positions or steps arelocated at regularly-spaced intervals, increasing or decreasingintervals, or irregular-spaced intervals on the one or more filaments.12. The device of claim 9, wherein the one or more filaments comprisesratcheting structure, ball and socket means, or bristle or line combelements to provide the series of discrete positions of steps.
 13. Thedevice of claim 9, wherein the one or more filaments comprise a helical,wavy, sinusoidal, triangular wave, square wave, or sawtooth shape.
 14. Arate-dependent, elastically-deformable device comprising: anelastically-deformable confinement member; a pair of opposing filamentsplaced inside the elastically-deformable confinement member, with oneend of each of the pair attached to opposite ends of theelastically-deformable confinement member and the other end of the eachof the pair unattached to the elastically-deformable confinement member;and a fluid that substantially fills the remaining volume inside theelastically-deformable confinement member, wherein the resistance forceto extension of the device changes the extension rate of the deviceincreases.
 15. The device of claim 14, wherein, when theelastically-deformable confinement member is in an undeformed state, thefilaments at least partially overlap one another.
 16. The device ofclaim 14, wherein the filaments are cables or ribbons.
 17. The device ofclaim 16, wherein the cable filaments are capable of intertwining witheach other, and the ribbon filaments are incapable of intertwining witheach other.
 18. The device of claim 14, wherein theelastically-deformable confinement member has anisotropic properties.19. The device of claim 14, wherein the elastically-deformableconfinement member has a higher resistance to radial extension comparedto its resistance to longitudinal extension.
 20. The device of claim 14,wherein the fluid is a Non-Newtonian fluid, non-shear thickening fluid.21. The device of claim 20, wherein the fluid is a shear thinning,thixotropic, rheopectic, a Bingham, viscoplastic, or viscoelastic fluid.22. A rate-dependent, elastically-deformable device comprising: anelastically-deformable confinement member; one or more filaments placedinside the elastically-deformable confinement member; and ashear-thickening fluid that substantially fills the remaining volumeinside the elastically-deformable confinement member, theshear-thickening fluid comprising a suspension of non-spherical solidparticles in a liquid, wherein the resistance force to extension of thedevice increases as the extension rate of the device increases.
 23. Thedevice of claim 22, wherein the non-spherical solid particles have anaspect ratio of about 2:1 or more.
 24. The device of claim 22, whereinthe non-spherical solid particles comprise precipitated calciumcarbonate (PCC) particles.